Surface mount package for long lead devices

ABSTRACT

Via holes are plated through the substrate of a surface mount package. The leads of an electronic device is inserted in the plated-through via holes. The bottom of the plated through metal is enlarged as pads to provide reliable soldering surfaces to a motherboard. Upon heating the leads are soldered to the walls of the plated through via holes. Alternatively, the leads can be folded before inserting into the plated-through via holes.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] This invention relates to package for electronic devices, inparticular to a surface mount package.

[0003] (2) Background of the Invention

[0004] Many kinds of electronic devices such as capacitors, resistorshave long leads. With the advent of printed circuits, it is desirable touse surface mount packages for the devices for easy connection to theprinted circuit board.

[0005]FIG. 1A shows top view of a conventional package for a typicallong lead device. A substrate 20 has two via holes 24 through which theleads of a device (not shown) can extend. FIG. 1B shows the side view ofsection A-A′ of FIG. 1A. The substrate 20 has two grooves 22 outside thevia holes 24. When the leads of a device is inserted through the viaholes, the leads are bent outward against the grooves 22 and recessed inthe grooves 22 as shown in FIG. 1C. FIG. 1D shows the side view of thepackage with a device 10 inserted through the package. The two leads 12of the device 10 are inserted through the substrate 20 and bent outward.Because of the recessed grooves 22, the bottom ends of the bent leads 12are flush with the bottom of the substrate 20. Thus the bottom surfaceof the package is flat for surface mounting to a printed circuit board.

[0006] However the rounded ends of the leads do not provide a bigcontact area for soldering to the printed circuit board, the solderingreliability. Although the ends of the leads 12 may be crimped flat toincrease the contact area, the increase in soldering, area is limited.

SUMMARY OF THE INVENTION

[0007] An object of this invention is provide a package for surfacemounting of long-lead electronic devices. Another object of thisinvention is to provide a big-area bonding pad for improving thesoldering reliability of a surface mount package.

[0008] These objects are achieved by using plated through via holes inthe substrate of the surface-mount package. The leads of the device areinserted into the plated through via holes. The bottom of the platedthrough metal is enlarged as a pad to provide a large reliable surfacemounting surface. Upon heating, the leads are soldered to the walls ofthe plated through holes. Alternatively, the leads of leads can befolded before inserting into the plated through holes.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

[0009]FIG. 1A shows a top view of a prior art surface mount package,FIG. 1B shows a section view of the package shown in FIG. 1A; FIG. 1Cshows the bottom view of the package shown in FIG. 1A; FIG. 1D shows theside view of the package when a long-lead device is mounted.

[0010]FIG. 2A shows the top view of the package of the presentinvention, FIG. 2B shows the section view of the package shown in FIG.2A; FIG. 2C shown the bottom view of the package shown in FIG. 2A; FIG.2D shows the side view of the package with a long-lead device mounted.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The top view of package of the present invention is shown in FIG.2A. The insulating substrate 30 of the package has two via holes 34. Thevia holes are plated through with soldering material 36 as shown in thesection view of the package FIG. 2B. The bottom of the plated-throughmetal 36 adheres to the bottom of the substrate 30 and is enlarged intoflat pads as shown in FIG. 2C. These enlarged bottom pads providereliable soldering contacts for surface mounting to a mother-board.

[0012]FIG. 2D shows the side view of the package with the leads 12 of along-lead device 10 inserted into the plated-through via holes of thesubstrate 30. Upon heating, the soldering material of plated-throughholes forms an intimate soldered contact with the long leads 12.Meanwhile, the enlarged bottom pads 36 of the plated-through via holescan form intimate soldered contacts with a motherboard (not shown).

[0013] The soldering material 36 for the via hole can be a tin-leadalloy, which melts upon heating.

[0014] If the long leads of the device 10 is very thin, the leads 22 ofthe device 10 can be folded inside the plated-through via hole 36 asshown in FIG. 2E. Folding provides more contact area of the leads 22with the plated-through 36.

[0015] While the preferred embodiment of the invention has beendescribed, it will be apparent to those skilled in the art that variousmodifications may be made in the embodiment for the surface mountpackage without departing from the spirit of the present invention. Suchmodifications are all within the scope of this invention.

1. A surface-mount package for an electronic device with at least onelong lead wire comprising: an insulating substrate; at least one viahole through said substrate for said lead wire to be inserted, andsoldering material plating along the wall of said via hole for solderingto said lead wire and extending into a flat soldering pad along thebottom of said substrate for surface mounting to a motherboard.
 2. Asurface mount package for an electronic device as described in claim 1,wherein there are two via holes.
 3. A surface mount package as describedin claim 1, wherein said lead wire is inserted to a depth no deeper thanthe thickness of the substrate.
 4. A surface mount package as describedin claim 1, wherein said lead wire is folded inside said via hole.
 5. Asurface mount package as described in claim 1, wherein said solderingmaterial is a tin-lead alloy.